Social Security isn't a very fertile topic for these guys because there are only a couple of ways to fix it, and they're both more mathematical than political. It is the most bipartisan of our challenges. Obama seems to be getting back into the debate, though. Same with Lehrer.

Unlike Medicare, where the candidates are going to argue about the mythical $716 billion cut to Medicare in Obamacare.

And Romney is right to focus on this. That money, which is supposed to come from cuts to providers, is almost certainly fictional. We've had a law that forces such cuts since 1997, and Congress has voted to avoid it every year since it was imposed.

It's not a cut to Medicare, but it is a fake funding source for Obamacare.

What of Ryan's voucher program?

This is a toughie. The voucher plan simultaneously made Paul Ryan the "serious thinker" in the Republican Party, but no one, not even Romney, actually wants to make seniors depend on vouchers rather than traditional Medicare.

So what are we talking about?

Even Romney now says he wants the voucher system as an option alongside the current program, which is an economic nightmare, since people will always pick whichever plan benefits them most, and thus costs society most.

But Romney does have a serious plan in this realm, and that's means-testing Medicare, and charging the rich more. We're probably going to have to do it, and he's the first one to willingly say it. So give Romney full credit on this.